Floating ball valve seal

ABSTRACT

A seal assembly is provided for a rotary ball valve an eccentric cammed ball. The seal assembly may include a seal ring disposed within the valve interior and biased toward the ball element of the valve. A seal ring retainer may be threadedly secured to an interior of the valve body, thereby retaining the seal ring in the valve body.

FIELD OF THE DISCLOSURE

The present disclosure generally relates seals for rotary ball controlvalves and, more particularly, to floating seals that are displaceablelaterally and axially.

BACKGROUND

Rotary ball valves are used in a wide number of process control systemapplications to control some parameters of a process fluid such as aliquid, gas, slurry, etc. While the process control system may use acontrol valve to ultimately control the pressure, level, pH, or otherdesired parameter of a fluid, the control valve basically controls therate of fluid flow.

Typically, a rotary ball valve includes a valve body defining a fluidinlet and a fluid outlet. A ball element is mounted in the valve bodyand rotates about an axis into and out of abutment with a seal assembly,thereby controlling the amount of fluid flow through the valve.

Rotary ball valve components, including the valve body, the ballelement, and the seal assembly, are typically constructed of metal. Thisstands especially true when used in high pressure and/or hightemperature applications. However, the ball element and seal assemblycan suffer wear due to the continuous engagement of the ball element andseal assembly during opening and closing of the valve. The problemsresulting from the wear include, but are not limited to, diminished lifespan of the valve components, increased frictional forces between theball element and the seal assembly, and undesirable leakage between theball element and the seal assembly, as well as between the seal assemblyand the valve body. Similarly, because the frictional forces tend toincrease as the components become more worn, the dynamic performance andcontrol characteristics within the valve are worsened, resulting ininefficiencies and inaccuracies in the valve. To alleviate some of theseconcerns, some seal assemblies are biased such as to provide a morereliable seal against the ball in the closed position.

SUMMARY

A seal assembly is provided for a rotary ball valve having an eccentriccammed ball. In one embodiment, the seal assembly may include a sealring disposed within the valve interior and biased toward the ballelement of the valve. A seal ring retainer may be threadedly secured toan interior of the valve body, thereby retaining the seal ring in thevalve body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a rotary ball valve constructed inaccordance with the principles of the present disclosure;

FIG. 2 is an enlarged fragmentary cross-sectional view taken at CircleII of FIG. 1 and illustrating an embodiment of the seal assembly of therotary ball valve with the rotary ball valve shown in the open position;and

FIG. 3 is another enlarged fragmentary cross-sectional view similar toFIG. 2 and showing the rotary ball valve in the closed position.

DETAILED DESCRIPTION

The floating ball valve seal described herein overcomes severalshortcomings of the prior art. The use of a C-seal extends the usefultemperature capability well above some of its counterparts which mustrely upon elastomeric seals for the secondary seal. However, the use ofan elastomeric seal (e.g., O-ring or spring-loaded face seal) is stillpossible when desired for cost or shutoff. The use of a face seal as asecondary seal provides the seal ring with the freedom to move axiallyand laterally. Providing the seal ring with the freedom to movelaterally gives the seal ring the ability to self adjust and tocompensate for any ball or seal misalignments due to machining orassembly tolerances. Reduced seal wear and improved shutoff result.

The seal ring can also move axially in a controlled and limited fashion,under the seating load imparted by a wave spring and limited by a sealring retainer, causing the ball and seal ring to break contact at somepoint in travel after the valve has moved from the fully closedposition. The contact between the ball and the seal is confined to aregion of the valve travel where the valve is fully closed, whichresults in reduced seal wear and improved shutoff.

FIG. 1 illustrates a rotary ball valve 10 constructed in accordance withthe principles of the disclosure, and generally including a valve body12, a bonnet 14, a control assembly 16, and a seal assembly 24. Thevalve body 12 includes an inlet 18, an outlet 20, a primary flowpath 22,and a bonnet opening 25. As indicated by the arrow, the primary flowpath22 extends from the inlet 18 to the outlet 20 in a direction that isgenerally parallel to a longitudinal axis A. The inlet 18 is surroundedby an inlet flange 26. The outlet 20 is surrounded by an outlet flange28. The inlet flange 26 and the outlet flange 28 are adapted to couplethe ball valve 10 into a process control pipeline such as by bolting,welding, clamping, or any other known means.

The control assembly 16 includes an eccentric cammed ball element 30, adrive shaft 32, and a support shaft 34. In one embodiment, the driveshaft 32 and the support shaft 34 are separated by a distance. In otherembodiments, the drive shaft 32 and the support shaft 34 may beintegrally formed as a single piece that extends from a through-bore 29to a blind bore 36. The ball element 30 has an axis of symmetry C thatis offset from the drive shaft axis B. As a result, a sealing surface 31of the ball element 30 rotates moves with a camming action (e.g., thesealing surface 31 displaces longitudinally, along axis A when the ballelement 31 rotates between a closed position and an open position).

As discussed above, the ball element 30 typically moves with a cammingaction to facilitate a repeatable seal with the seal assembly 24 when inthe closed position, as shown in FIG. 1. More specifically, the exterioror sealing surface 31 of the ball element 30 may define a portion of asphere, all points on the exterior surface of the ball element not beingequidistant from a natural pivot point (i.e., axis C) of the ballelement 30.

To accommodate the seal assembly 24, the disclosed embodiment of thevalve body 12 includes an internal recess 42 disposed downstream fromthe inlet 18. The internal recess 42 is disposed between the outlet 20and the ball element 30 of the control assembly 16. The internal recess42 may have a generally annular shape including an annular surface 38and a transverse surface 40.

Referring now to FIG. 2, which is a detailed view taken from Circle IIof FIG. 1, one specific embodiment of a seal assembly 24 constructed inaccordance with the teachings of the present disclosure will bedescribed.

The seal assembly 24 includes a seal ring 44 disposed within theinterior of the valve body 12. The seal ring 44 is biased toward theball element to sealingly engage the ball element 30. A seal ringretainer 46 is located downstream of the seal ring 44 and retains theseal ring 44 within the internal recess 42. A secondary leak path 50 isformed between the seal ring 44 and the valve body 12. The secondaryleak path 50 is exposed to fluid pressure from fluid flowing through therotary ball valve 10. A first auxiliary seal, such as a C-seal 54, maybe disposed between the seal ring 44 and the valve body 12 to preventfluid flow through the secondary leak path 50.

As discussed above, the seal ring 44 of the seal assembly 24 isgenerally annular in shape and may be machined from a wear-resistantmetal, such as Alloy 6 or stainless steel with Alloy 6 hardfacing, forexample. As illustrated in the cross-sectional view of FIG. 2, the sealring 44 may be defined laterally by a cylindrical seal inner wall 58 anda cylindrical seal outer wall 60, and a seal upstream wall 62 may extendfrom the seal outer wall 60 towards the inner wall 58 in a radialdirection. A seal ring protrusion 64 may extend from the seal upstreamwall 62, and the seal ring protrusion 64 may include by a cylindricalside protrusion wall 66 that may extend from the seal upstream wall 62in an axial direction (i.e., a direction parallel to the longitudinalaxis A). An end wall 68 may extend from the side protrusion wall 66 in adirection parallel to the seal upstream wall 62. A ball engagementsurface 70 may extend between the end wall 68 and the seal inner wall58, and the ball engagement surface 70 may be concave in shape, orcomplementary to the sealing surface 31 of the ball element 30. Morespecifically, the ball engagement surface 70 may be contoured to matewith a corresponding portion of the sealing surface 31 of the ballelement 30 so that when the rotary ball valve 10 is moved into theclosed, or seated, position, the ball engagement surface 70 of the sealring 44 sealingly engages the sealing surface 31 of the ball element 30.In one embodiment, the ball engagement surface may be partiallyspherical and concave in shape. The ball engagement surface 70 may behardfaced to enhance seal cycle life and to prevent seat line galling.

The seal ring 44 also includes an annular inner recess 72 and an annularspring recess 74 disposed between the seal inner wall 58 and the sealouter wall 60. The inner recess 72 and the spring recess 74 may eachhave a generally rectangular cross-sectional shape and may be adjacentlydisposed such that an inner ridge 76, an intermediate ridge 78, and anouter ridge 80 are formed in the seal ring 44. However, both the innerrecess 72 and the spring recess 74 may have any shape or combination ofshapes suitable for a particular application. A bottom portion of eachof the inner ridge 76, intermediate ridge 78, and the outer ridge 80 maybe axially equidistant from the plane defining the seal downstream wall62. The inner recess 72 may be sized and shaped to receive the firstauxiliary seal 54. The spring recess 74 may be sized and shaped toreceive a resilient element, such as the wave spring 84.

As illustrated in FIGS. 2 and 3, the seal assembly 24 may also includethe annular seal ring retainer 46, which secures the seal ring 44 withinthe recess 42 in the valve body 12. The seal retainer 46 may be machinedfrom a corrosion-resistant metal, such as stainless steel, for example.The seal retainer 46 may have an “L” cross-sectional shape, including acylindrical retainer inner wall 120 and a cylindrical retainer outerwall 122 that each extend in a generally axial direction. A retainerupstream wall 124 and a retainer downstream wall 126 that is parallel toand axially offset from the upstream wall 124 may extend in a generallyradial or lateral direction from the retainer outer wall 122 to furtherdefine the seal retainer 46. A recess 128 may be formed between thecylindrical retainer inner wall 120 and the retainer upstream wall 124to provide clearance for the ball element 30. The cylindrical retainerouter wall 122 may include threads 130 that cooperate with correspondingthreads 132 on the valve body 12.

A distance from the retainer downstream wall 126 to the transversesurface 40 may be greater than a length of the seal ring outer wall 60.As a result, the seal ring 44 is displaceable in a longitudinaldirection, generally parallel to axis A. Thus, the ball engagementsurface 70 engages the sealing surface 31 of the ball element 30 beforethe ball element 30 is rotated to the fully closed position due to thecamming action of the ball element 30. More specifically, the seal ringretainer 46 may limit axial displacement of the seal ring 44 to only theangular rotation of the ball element 30 that effects closure of thevalve (e.g., less than 20° of rotation from a fully closed position).The seal ring 44 may displace longitudinally slightly to accommodate theremaining camming action of the ball element 30. In this manner, theseal ring 44 cushions the contact between the ball engagement surface 70and the sealing surface 31, which minimizes mechanical damage to eithersurface during closing of the ball element 30.

Similarly, the transverse surface 40 is longer than an overall width Wof the seal ring 44. As a result, the seal ring 44 is displaceableradially or laterally, towards the annular surface 38 to account formisalignment of the ball element 30 and/or machining errors that arewithin acceptable tolerances. The seal ring outer wall 60 may contactthe annular surface 38 to prevent further radial or lateral movement ofthe seal ring 44. In other embodiments, the retainer inner wall 120 mayform a stop by physically preventing the cylindrical side protrusionwall 66 from moving further towards the annular surface 38.

By trapping the seal ring 44 between the seal ring retainer 46 and thetransverse surface 40 of the valve body 12, a size of the seal assembly24 may be minimized in a longitudinal direction, thereby reducing theoverall size of the valve 10.

In order to seal the secondary leak path 50, a mouth of the C-seal 54may face the general flow path of fluid passing through the secondaryleak path 50 such that process fluid flowing through the secondary leakpath 50 enters the mouth of the C-seal 54. In the embodiment illustratedin FIG. 2, the mouth of the C-seal 54 may face the inner ridge 76 of theseal ring 44. The C-seal 54 may be dimensioned such that when the valve10 is in the open position (as illustrated in FIG. 2) and the seal ring44 contacts the retainer downstream wall 126, a portion of the exteriorof the C-seal 54 does not contact the transverse surface 40 of the valvebody 12. Accordingly, when the ball element 30 is in the open position,a portion of the process fluid may flow through the secondary leak path50 between the exterior of the C-seal 54 and the transverse surface 40without entering the mouth of the C-seal 54.

When the ball element 30 is moved into the closed position (FIG. 3), theball element 30 contacts the ball engagement surface 70 of the seal ring44 and displaces the seal ring 44 towards the transverse surface 40 ofthe valve body 12. As the seal ring 44 is displaced, the distancebetween the top surface of the inner recess 72 of the seal ring 44 andthe transverse surface 40 of the valve body 12 is reduced such that theexterior of the C-seal 54 may contact the transverse surface 40, theinner recess 72, and the intermediate ridge 78 of the seal ring 44. Dueto the displacement, the C-seal 54 is compressed such that the outersurface of the C-seal 54 sealingly engages the transverse surface 40,thereby preventing process fluid from flowing between the seal ring 44and the valve body 12 downstream of the C-seal 54. In this manner, theC-seal 54 seals the secondary leak path 50.

Because the C-seal 54 moves with the seal ring 44 relative to the valvebody 12 as the ball element 30 engages with and disengages from the sealring 44, the C-seal 54 is referred to as a dynamic C-seal. The dynamicC-seal 54 may be fabricated from a corrosion-resistant metal, such asN07718 (Inconel 718). Because the dynamic C-seal 54 is made of metal,the rotary ball valve 10 can operate at higher temperatures than valvesusing elastomeric seals.

To install the seal assembly 24 to the valve body 12, the seal assembly24 the C-seal 54 is first placed in the inner recess 72 of the seal ring44 in the manner previously described, and a resilient element such asthe wave spring 84 is placed in the spring recess 74 in the mannerpreviously described. The seal ring 44 is then placed in the valve body12 in the recess 42, and the seal retainer 46 is placed over the sealring 44. The seal ring retainer 46 may then be rotated into threadedengagement with the corresponding threads on the valve body 12 to securethe seal retainer 46 to the valve body 12. Once assembled, the seal ring44 may not be initially be positioned to ensure a proper seal betweenthe ball engagement surface 70 of the seal ring 44 and a portion of thesealing surface 31 of the ball element 30. However, due to theself-aligning property of the seal ring 44 previously described (e.g.,the ability to displace both axially and radially), the ball element 30will axially and radially displace the seal ring 44 as the ball element30 contacts the ball engagement surface 70 during the closing of therotary ball valve 10.

While various embodiments have been described above, this disclosure isnot intended to be limited thereto. Variations can be made to thedisclosed embodiments that are still within the scope of the appendedclaims.

1.-13. (canceled)
 14. A seal ring assembly comprising: a seal ringadapted to be disposed within a valve interior and that is adapted to bebiased towards a ball element, wherein the seal ring is adapted tosealingly engage the ball element; and a seal ring retainer includingthreads in an outer wall that are adapted to be threadedly securedwithin a recess in the valve body, the seal ring retainer adapted to beremovably secured to the valve body by a threaded connection, whereinthe seal ring is movable both axially and radially within the valvebody.
 15. The seal assembly of claim 14, wherein the seal ring includesa partially spherical concave sealing surface.
 16. The seal assembly ofclaim 14, wherein the seal ring includes an inner recess and a springrecess.
 17. The seal assembly of claim 16, further comprising a c-sealdisposed in the inner recess.
 18. The seal assembly of claim 16, furthercomprising a biasing element disposed in the spring recess.
 19. The sealassembly of claim 16, wherein the seal ring includes a cylindrical innerwall, a cylindrical outer wall, and a seal upstream wall.
 20. The sealassembly of claim 19, wherein the seal ring includes a seal ringprotrusion extending from the seal upstream wall.
 21. The seal assemblyof claim 16, wherein the seal ring retainer is L-shaped when viewed incross-section.